The present invention relates generally to improved methods and systems for structurally enhancing attachments and reinforcing members used in the manufacture of automotive vehicles. More particularly, the invention relates to an extrusion reinforcement system integrated along with an automotive reinforcement surface or substrate, such as a rocker reinforcement, wherein an expandable material is placed along stand-offs or bolt attachments securing the extrusion to the desired substrate. Upon activation of the expandable material, the material expands and forms a structural bond between the reinforcement substrate and the extrusion resulting in the improvement of structurally integrity of the extrusion application area and the reduction of labor demand and manufacturing processes required to secure the extrusion in place.
Traditional automotive manufacturing operations often rely on the use of high-strength extrusions for placement in certain areas of the vehicle to improve structural stiffness and rigidity of the chosen area or application of the vehicle. Generally speaking, these prior art techniques employ the use of an extrusion consisting of one or more closed sections which are either bolted or welded to a vehicle mating panel or substrate, such as a rocker reinforcement, and are further characterized by having stand-offs as part of the extrusion which allow the extrusion to maintain a desired torque when bolted or welded to the panel or substrate. Typically, this step or process involves the use of purely localized bolt attachments at certain points throughout the extrusion which may result in non-uniform reinforcement. This process also requires the vehicle manufacturer to allocate tooling, floor space, and added labor in the manufacturing facility to either weld or both the extrusion to the desired automotive application.
While these prior art devices perform well and are advantageous in many circumstances, they often require a large capital and labor investment to integrate the bolted or welded extrusion into the chosen manufacturing facility, utilize a large amount of floor space and maintenance resources at the vehicle assembly plant, and require an additional manufacturing process and labor demand. In turn, the manufacturer is required to devote both financial and technical resources to develop tooling for the bolted or welded extrusion and is required to test the structure to determine if the localized bolt attachments or welds are optimally placed for structural reinforcement, which adds potential cost and delay, particularly if changes to the vehicle structure are implemented during the design stages.
Accordingly, there is need for a simple low cost system that provides an integrated extrusion having an expandable or structurally reinforcing material placed along the extrusion which expands and fills to form a structural bond between the extrusion and the automotive substrate, and which can be employed across a wide range of different sizes or shapes of extrusions.
The present invention is directed to a structural reinforcement system which can be integrated with an aluminum extrusion, and particularly one for automotive vehicle space frame structures, such as (without limitation) rocker reinforcements, vehicle door beam assemblies, vehicle roof and pillar assemblies. The system generally employs extrusion techniques in the form of a mini-applicator technology for facilitating the application of an expandable and structurally reinforcing material onto the extrusion through an extrude-in-place process. It is contemplated that the material disclosed in the present invention functions as an anti-vibration dampener and structural reinforcement when expanded and bonded from the surface of the extrusion to the chosen automotive substrate, such as a rocker reinforcement, when the rocker reinforcement (now attached to the vehicle in the assembly operation), is processed through e-coat and paint cycles in a vehicle assembly plant. In one embodiment, the material is heat expandable and at least partially fills the gap which may exist between the extrusion and rocker by cross-linking and structurally adhering the extrusion and the rocker reinforcement during the painting operation thereby reducing noise and vibration characteristics of the vehicle as well as structurally reinforcing the vehicle and the rocker reinforcement. In another embodiment, the material is a melt-flow material, and upon the application of heat will spread over the surface of the extrusion thereby providing a uniform flow and reinforcement along any seam, gap, or cavity that may exist between a traditional extrusion bolted or welded on the rocker reinforcement.
In a particular preferred embodiment, the expandable material or medium comprises at least one strip applied along the surface of an aluminum extrusion between the extrusion stand-offs and any bolt attachment means in a solid (though pliable) form in accordance with the teachings of commonly owned U.S. Pat. No. 5,358,397 (xe2x80x9cApparatus For Extruding Flowable Materialsxe2x80x9d), hereby expressly incorporated by reference. The expandable material or medium is at least partially coated with an active polymer having structural reinforcement characteristics or other heat activated polymer, (e.g., a formable hot melt adhesive based polymer or an expandable structural foam, examples of which include olefinic polymers, vinyl polymers, thermoplastic rubber-containing polymers, epoxies, urethanes or the like). The strip of material then expands from the surface of the extrusion and bonds to the rocker reinforcement of the vehicle when exposed to the e-coat process as well as other paint operation cycles encountered in a final vehicle assembly facility.
In a particular non-limiting embodiment, a plurality of strips comprised of the expandable material or medium are transformed from a solid or dry chemical state to a visco-elastic stage through the use of a mini-applicator which processes the strips at a temperature sufficient to transform the strips into a visco-elastic material capable of flowing onto the external surface of an aluminum extrusion in a desired consistency, thickness, and pattern.
The heat application and other shear functions from the mini-applicator allows the material to flow in a uniform shape and manner as it is placed onto an external surface of the extrusion where it bonds. Once applied to the external service of the extrusion by the mini-applicator and no longer exposed to the heat source emanating from the mini-applicator, the material returns to it solid or dry chemical state and thereby remains in place along the extrusion. The extrusion is then mounted within a rocker assembly or other automotive application by the vehicle manufacture in accordance with manufacturing techniques that are well known in the art. As the rocker assembly is prepared for final assembly of the vehicle, it is processed through e-coat and other heat-inducing paint operations which result in expansion and bonding of the material from the extrusion to an outer surface portion of the rocker assembly where it cures and remains in place. It is contemplated that the material expands from the external surface of the extrusion and cross-links to the rocker substrates in structural adherence serving to reduce the noise and vibration emanating from the rocker assembly and, more particularly, providing structural reinforcement to the rocker assembly. Although the preferred embodiment discloses the material essentially chemically cross-linking and structurally adhering from the external surface of the extrusion into contact with the rocker assembly in the configuration of a strip placed along the surface of the extrusion, it will be appreciated that various patterns and applications of the material along the extrusion would allow the material to expand and chemically cross-link with either or both of the extrusion and the rocker assembly as well as any other substrate that may be utilized or encountered in an automotive structural reinforcement application or other application which would facilitate either passenger of cargo access to a vehicle.
In one embodiment the expandable material or medium is placed onto the exterior surface of an aluminum extrusion in a continuous or non-continuous manner adjacent to one or more gaps or walls defining a cavity between the extrusion and an automotive rocker assembly. The expandable material or medium is activated to accomplish transformation (e.g., expansion or flow) of the active polymer or polymer within the gap after the extrusion is mounted onto the vehicle and the vehicle is exposed to heat as it is processed through the e-coat and paint operation cycles of a final automotive assembly plant, which is well known in the art. The resulting structure includes a wall or expansive extrusion that is coated over at least a portion of its surface with the expandable material acting to reduce vibration during transport and provide structural reinforcement, stiffness, and rigidity to the rocker assembly. It will be appreciated that a preferred expandable material would consist of a material comprising a number of chemical formulations including, but not limited to, metal (such as steel, aluminum, etc.), rubber (such as a butyl or isobutylene polymer, copolymer, or similar elastomer having good dampening and reinforcement characteristics), and plastic polymer chemistry (ideally material that would remain rigid at temperatures generally encountered by an automotive body skin during operation of the vehicle, for example xe2x88x9240xc2x0 C. to 190xc2x0 C.